Teriparatide Administration Increases Periprosthetic Bone Mineral Density After Total Knee Arthroplasty: A Prospective Study

Background

Teriparatide is a currently available therapeutic agent for osteoporosis. Previous studies have reported that teriparatide affects periprosthetic bone mineral density (BMD) after total knee arthroplasty (TKA). However, little agreement has been reached concerning the treatment of periprosthetic BMD after TKA with teriparatide. Moreover, BMD in the femoral and tibial sides of the joints together has never been examined. We investigated the efficacy of teriparatide to inhibit BMD loss in the femoral and tibial side and considered complications such as migration and periprosthetic fractures after TKA.

全膝关节置换术治疗膝外翻畸形疗效观察

目的探讨膝外翻畸形患者施行全膝关节置换的手术方法和临床疗效。方法 2001年7月至2008年6月收治膝外翻畸形患者25例29膝,男5例,女20例;年龄55-75岁,平均64.3岁。手术采用髌旁内侧入路,模具引导下截骨,按Whiteside方法进行外侧软组织松解,采用后方稳定型假体。对比手术前、后股胫角变化,采用KSS评分评价手术疗效。结果 1例患者住院期间发生深静脉血栓,经溶栓治疗后症状消失。全部患者获12-48个月随访,无感染、腓总神经损伤、髌骨脱位、膝关节不稳等并发症。术后12个月平均股胫角（7.42±1.80）°,KSS临床评分（82.47±5.38）分,功能评分（86.47±4.83）分,与术前比较有统计学意义（P〈0.05）。结论膝外翻畸形施行全膝关节置换手术,术中正确截骨,合理软组织松解,保持髌骨良好运行轨迹,防止腓总神经损伤,可以获得满意疗效。     

Bone Mineral Density of the Femur in Autopsy Retrieved Total Knee Arthroplasties

Bone mineral density (BMD), as measured by DEXA, can vary depending on bone rotation and fat content of soft tissues. We performed DEXA measurements, under controlled positioning, on 24 autopsy-retrieved femora from patients who had fully functional and asymptomatic successful TKA to determine periprosthetic BMD changes and compared results to 24 normal cadaveric femora. In TKA specimens, BMD was affected by gender, preoperative diagnosis, and zone under analysis. The lowest mean BMD was in the anterior femoral condylar zone. Males had higher mean BMD at all zones while patients with preoperative diagnosis of osteoarthritis had higher BMD in the posterior condylar zone. The mean BMD in the anterior femoral condylar zone in TKA specimens was significantly lower than in normal specimens without arthroplasties, most likely due to stress shielding.     

The Position of the Tibial Component Affecting the Postoperative Mechanical Axis in Total Knee Arthroplasty

The purpose is to identify whether the position of the tibial component in relation to the anatomical axis affects the postoperative mechanical axis in total knee arthroplasty for Korean patients. Preoperatively, 30 patients with varus deformity lesser than 10° were classified as group A, and 30 patients greater than 10° were classified as group B. Postoperatively, the distance between the midline of the tibial stem and anatomical axis (medial offset) was measured. The medial offsets were 2.5 ± 1.9 mm in group A and 3.9 ± 2.7 mm in group B (P = .021). The postoperative mechanical axes were varus 1.3 ± 1.2° in group A and varus 2.5 ± 2.0° in group B (P = .004). We think that the medial position of tibial component in relation to the anatomical axis affects the measurement of postoperative mechanical axis in total knee arthroplasty.     

Changes in Bone Mineral Density of Both Proximal Femurs after Total Knee Arthroplasty

Background

This study investigated the effects of total knee arthroplasty (TKA) on bone mineral density (BMD) of the proximal femur in patients who underwent the procedure.

Methods

Forty-eight patients scheduled to undergo unilateral TKA because of primary knee osteoarthritis were included in this study, which was conducted at a medical center between October 2006 and October 2009. In these 48 patients, 96 hips were evaluated. Measurement of BMD was performed preoperatively and one month, three months, six months, and one year after unilateral TKA. Repeated measured analysis of variance and paired t-tests for comparison of two repeated samples were used to compare differences between time points (preoperation, one, three, six, and 12 months) and between the operative and nonoperative sides.

Results

Preoperatively, BMD of the femoral neck, trochanter, and total hip on the operative side were lower than on the nonoperative side; however, there was no statistical difference. BMD of both femoral neck areas was significantly lower than preoperative BMD at one month and three months after TKA. BMD of both trochanter areas was significantly lower than preoperative BMD at one month and three months after TKA. BMD of both total hips was significantly lower than preoperative BMD at three months after TKA. However, no statistical differences of changes in BMD were observed between the operative and nonoperative sides at each measurement time.

Conclusions

According to our results, TKA was found to affect both proximal femurs during the acute period. However, TKA did not affect a change in BMD of the proximal femur during one year postoperative.     

人工膝关节置换治疗膝外翻畸形的疗效

目的探讨全膝关节置换治疗膝关节外翻畸形的技术方法和临床效果。方法 2006年2月至2010年4月收治12例12膝外翻畸形患者,8例骨关节炎和4例类风湿性关节炎,应用人工全膝关节置换手术治疗。根据X线片比较术前和术后膝外翻角度,应用HSS膝关节评分系统进行临床效果评价。结果术后切口均一期愈合,无感染,无腓总神经麻痹发生;随访6~34个月,平均19个月;术前膝外翻角度13°~35°,平均(19.8±3.3)°,术后膝外翻角度4.9°~9.5°,平均(6.4±1.4)°,与术前比较差异有统计学意义(P0.05);术前HSS评分为31~63分,平均(38.0±2.7)分,术后末次随访膝关节HSS评分为78~89分,平均(84.0±2.9)分,与术前比较差异有统计学意义(P0.05)。结论人工全膝关节置换是膝关节炎合并外翻畸形的有效治疗方法。     

Computed Tomography Evaluation in Total Knee Arthroplasty: Computer-Assisted Navigation Versus Conventional Instrumentation in Patients With Advanced Valgus Arthritic Knees

Arthritic knees with advanced valgus deformity present with soft tissue and osseous anomalies that make total knee arthroplasty (TKA) difficult. We conducted a retrospective chart review of 41 patients (51 knees) to determine whether computer-assisted surgery-TKA (CAS-TKA) is superior to TKA using conventional guiding systems. A significantly higher rate of lateral retinaculum release as well as outlier of sagittal mechanical axes and position of the femoral component (femoral flexion and femoral rotational angle) was recorded in the conventional TKA group versus the CAS-TKA group. Both groups had significant postoperative improvement in clinical performance, but results did not differ significantly between groups. Despite its radiographic benefit, CAS-TKA showed no significant benefit over TKA in short-term clinical functional outcomes when performed by an experienced surgeon.     

Radiolucent Casting Tape Allows for Accurate Measurement of Forearm Bone Mineral Density Using Dual-Energy X-ray Absorptiometry

The ability to perform dual-energy X-ray absorptiometry (DXA) while a patient is in a cast would give investigators the opportunity to follow early changes in bone mineral density (BMD, g/cm2) during fracture healing or to evaluate bone changes related to immobilization. The objective of this study was to determine if accurate and precise DXA scans could be obtained through polyester-based radiolucent casting tape (Delta-Cast Elite [DCE], Johnson & Johnson, Inc., Raynham, MA) and standard fiberglass casting tape (Delta Lite [DL], Johnson & Johnson, Inc.). DXA scans were performed using a Lunar DPXL densitometer. Standard forearm regions of interest were analyzed. Ten normal volunteers had three consecutive scans of their dominant arm with no cast, with a radiolucent (DCE) cast, and with a fiberglass (DL) cast. Precision was calculated using data from three volunteers (three scans each; no cast, DCE, DL). Results of DCE and DL were compared with results with no cast. In a second series, a spine phantom was placed inside rice-filled forearm casts and repetitively scanned; results with DCE and DL were compared with the mean BMD values for the phantom alone. Analyses of the scans through the DL casts were difficult because the radiodensity of the fiberglass interfered with edge detection. This problem was exacerbated by low BMD (i.e., scans for women). Edge detection was not a problem with the DCE scans. Although the group mean BMD values with in vivo no cast, DCE, or DL scans were similar for all regions of interest, the data obtained for ultradistal regions of interest with DL scans were less precise. BMD values for the fiberglass-encased phantom were significantly lower compared with no cast or DCE scans (p = 0.0002). This study demonstrates that it is possible to perform accurate and precise forearm DXA scans through polyester-based radiolucent DCE casting tape.     

Changes in Bone Mineral Density of the Acetabulum and Proximal Femur After Total Hip Resurfacing Arthroplasty

Our aim was to investigate the changes in bone mineral density (BMD) of acetabulum and proximal femur after total hip resurfacing arthroplasty. A comparative study was carried out on 51 hips in 48 patients. Group A consisted of 25 patients (26 hips) who had undergone total hip resurfacing and group B consisted of 23 patients (25 hips) who had had large-diameter metal-on-metal total hip arthroplasty (THA). BMDs around the acetabulum and proximal femur were measured using dual-energy x-ray absorptiometry (DEXA) at 2 weeks, 6 months, 1 year and annually thereafter during the 3 years after surgery. At final follow-up, the acetabular net mean BMD decreased by 11% in group A and 10% in group B with no differences between two groups (P = .35). For the femoral side, in Gruen zone 1, the mean BMD increased by 4% in group A, whereas it decreased by 11% in group B (P = .029). In Gruen zone 7, the mean BMD increased by 8% at the final follow-up in group A, whereas it decreased by 13% in group B (P = .02). In both groups the mean BMD increased by 3% in Gruen zones 3, 4, 5, and 6. Stress-related bone loss of the acetabulum was comparable for MOM THA and resurfacing devices, but proximal femoral bone density increased in the resurfacing group and decreased in the THA group.     

Bone Mineral Density in the Proximal Femur and Contralateral Knee After Total Knee Arthroplasty

Osteoarthrosis (OA) is often associated with pain and disability, which are relieved after total knee arthroplasty (TKA), but the nature of bone changes associated with OA is controversial. We examined preoperative hip and contralateral knee bone mineral density (BMD) in patients requiring TKA and monitored the BMD changes postoperatively. Sixty-nine patients, scheduled to have TKA for osteoarthrotic knees, had both hips and contralateral knee BMD measured by dual-energy X-ray absorptiometry (DXA) at the time of operation (baseline) and at 1 yr after operation. X-rays of the knee joints were also taken to evaluate the severity of OA. Preoperatively, 27% and 38% of the patients had total hip BMD Z-score more than 1 SD in the operated side and contralateral hips, respectively. In all regions of interest (ROI), the mean baseline BMD of the affected side proximal femur was significantly lower than that of the contralateral side (p < 0.0005-0.019). The severity of OA was not associated with BMD. During 1-yr follow-up, the postoperative knee status and the physical activity of the patients (AKS score) improved. However, neither the hip nor the nonoperated knee BMDs increased. Knee OA is associated with significantly lower BMD values in the affected side compared with the contralateral hip, and these levels remained similar or decreased during a 1-yr follow-up. We conclude that improved mobility after TKA does not improve the effects of preoperative disuse-associated bone loss in the short term.     

Peripheral Nerve Blocks vs Periarticular Injections in Total Knee Arthroplasty

In patients undergoing surgery, optimal pain management is associated with improved perioperative outcomes, patient satisfaction with surgery, and a more rapid functional recovery. In recent years, the employment of multimodal pain management strategies has become increasingly widespread. In particular, there has been an explosion in the use of peripheral nerve blockade and periarticular injections in total knee arthroplasty. However, there is significant variability in the administration of either modality of anesthesia. As such, a critical evaluation of the current literature is warranted to elucidate the advantages and disadvantages of each technique with the ultimate goal of further refining current pain control strategies. In this symposium, we review each of these modalities and their association with pain management, narcotic consumption, length of hospital stay, and adverse events.     

Lateral Epicondylar Osteotomy Using Computer Navigation in Total Knee Arthroplasty for Rigid Valgus Deformities

Extensive release of posterolateral structures may be required to correct rigid and severe valgus deformities during total knee arthroplasty. Current techniques are technically difficult, may not accurately restore soft tissue balance, and are associated with postoperative complications. Computer navigation while performing lateral femoral epicondylar osteotomy allows precise, controlled, quantitative lengthening of lateral structures and restoration of optimum soft tissue balance and alignment.     

Robot-Assisted Total Knee Arthroplasty Accurately Restores the Joint Line and Mechanical Axis. A Prospective Randomised Study

Robot-assisted Total Knee Arthroplasty (TKA) improves the accuracy and precision of component implantation and mechanical axis (MA) alignment. Joint-line restoration in robot-assisted TKA is not widely described and joint-line deviation of > 5 mm results in mid-flexion instability and poor outcomes. We prospectively randomised 60 patients into two groups: 31 patients (robot-assisted), 29 patients (conventional). No MA outliers (> ± 3° from neutral) or notching was noted in the robot-assisted group as compared with 19.4% (P = 0.049) and 10.3% (P = 0.238) respectively in the conventional group. The robot-assisted group had 3.23% joint-line outliers (> 5 mm) as compared to 20.6% in the conventional group (P = 0.049). Robot-assisted TKA produces similar short-term clinical outcomes when compared to conventional methods with reduction of MA alignment and joint-line deviation outliers.     

Predicting the Feasibility of Correcting Mechanical Axis in Large Varus Deformities With Unicompartmental Knee Arthroplasty

Background

Due to disappointing historical outcomes of unicompartmental knee arthroplasty (UKA), Kozinn and Scott proposed strict selection criteria, including preoperative varus alignment of ≤15°, to improve the outcomes of UKA. No studies to date, however, have assessed the feasibility of correcting large preoperative varus deformities with UKA surgery. The study goals were therefore to (1) assess to what extent patients with large varus deformities could be corrected and (2) determine radiographic parameters to predict sufficient correction.

Porous Tantalum Tibial Component Prevents Periprosthetic Loss of Bone Mineral Density After Total Knee Arthroplasty for Five Years—A Matched Cohort Study

In 21 knees receiving porous tantalum tibial component and 21 knees receiving a cemented cobalt-chromium tibial component, dual x-ray absorptiometry scans were performed for five years post-operatively. The postoperative decrease in the bone mineral density in the lateral aspect of the tibia was significantly less in knees with porous tantalum tibial components (11.6%) than in knees with cemented cobalt-chromium tibial components (29.6%) at five years (p < 0.05). No prosthetic migration or periprosthetic fracture was detected in either group. The present study is one of the studies with the longest follow-up period on bone mineral density after total knee arthroplasty. Porous tantalum tibial component has a favorable effect on the bone mineral density of the proximal tibia after total knee arthroplasty up to five years.     

The Biomechanical Effect of Increased Valgus on Total Knee Arthroplasty: A Cadaveric Study

The effects of valgus load on cadaveric knees following total knee arthroplasty (TKA) were investigated using a custom testing system. TKAs were performed on 8 cadaveric knees and tested at 0°, 30°, and 60° knee flexion in both neutral and 5° valgus. Fuji pressure sensitive film was used to quantify contact areas and pressures and MCL strain was determined using a Microscribe digitizing system. Lateral tibiofemoral pressures increased (P < 0.05) at all knee flexion angles with valgus loading. Patellofemoral contact characteristics did not change significantly (P > 0.05). Significant increases in strain were observed along the anterior and posterior border of the MCL at all knee flexion angles. These findings suggest that valgus loading increases TKA joint contact pressures and MCL strain with increasing knee flexion which may increase implant instability.     

Accuracy of Implant Positioning for Minimally Invasive Total Knee Arthroplasty in Patients With Severe Varus Deformity

Minimally invasive surgery (MIS) in total knee arthroplasty (TKA) reportedly yields decreased patient morbidity and a rapid return of function, but how much deformity can be accepted for MIS-TKA remains unclear. This study investigated 238 knees from 218 consecutive patients who underwent MIS-TKA. Patients were divided into groups with tibiofemoral mechanical axis (TFM) 195° or greater and TFM less than 195°, then clinical and radiographic results were compared. Similar improvements in knee score at 3 months postoperatively were obtained in the both groups, whereas radiographic accuracy of the coronal alignment in the TFM ≥195° group was inferior to that in TFM <195° group. Postoperative TFM was significantly worsened in patients with lateral bowing angle of the femoral shaft (LBFS) 4° or greater, and 53% of patients in the TFM ≥195° group displayed LBFS 4° or greater, explaining the inferior radiographic accuracy in this group compared with the TFM <195° group. These results indicate that use of MIS techniques decreases radiographic accuracy, particularly in patients with severe genu varum and increased LBFS.